ISO MPEG standards group is in the process of defining a Real Time Interface (RTI) specification for video encoders/decoders which constrains the real-time byte delivery schedule of transport bit-streams to real decoders. A real time decoder model includes three (3) buffers for each elementary video bit-stream: the transport buffer, the multiplexing buffer and an elementary bit-stream buffer. These buffers are intended to be sized to take into account the fact that bytes in the elementary bit-stream will arrive at a decoder with some jitter. When the video bit-stream has been transmitted over an Asynchronous Transport Mode (ATM) network, the jitter is referred to as Cell Delay Variation (CDV).
Transform coding techniques and other systems for compressing video motion pictures are well known. Specifically, in our article entitled "Constraints on Variable Bit-Rate Video for ATM Networks", IEEE Transactions on Circuits and Systems for Video Technology, Volume 2, Number 4, pages 361-372, December 1992, we indicated that, assuming no delay jitter, the encoder could prevent decoder buffer overflow and underflow by computing the actual decoder buffer fullness. (Also see our U.S. Pat. No. 5,159,447 issued Oct. 27, 1992.)
Additionally, in our standards contribution entitled "Timing Recovery for Variable Bit-Rate Video on ATM Networks", MPEG92/396, AVC-315, Paris France, Jul. 3, 1992, we disclosed a decoder which, in the presence of jitter, prevents decoder buffer overflow and underflow by incorporating additional delay and additional decoder buffer capacity. (Also see our U.S. Pat. No. 5,287,182 issued Feb. 15, 1994.) Given guaranteed bounds on jitter, decoder buffer overflow and underflow could be eliminated by chosing sufficiently large buffers and sufficiently large jitter delay. This solution can be thought of as having the decoder use its available buffer capacity to shift the so-called Video Buffer Verifier (VBV) to ensure that there is no buffer overflow or underflow. In practice, the decoder buffer may not have enough capacity to absorb both the VBV fluctuations and the jitter. In addition, it incurs additional decoding delay, and is practical only for the elementary bit-stream decoder buffer.